1. Field of the Invention
The present invention relates to a magnetic head supporting mechanism used for a magnetic disk drive.
2. Description of the Related Art
A magnetic head slider on which a magnetic head is mounted is attached to a free end of a load beam, and is maintained, during a recording/reproducing operation, in a state in which the magnetic head slider flies above a magnetic disk.
Recently, it has been required to improve an HDI (Head Disk Interface) characteristic, which is one of the parameters describing the reliability of magnetic disk drives. In order to meet the above requirement, it is nessary to diminish the mass of the magnetic head slider or reduce a spring force urging the magnetic head slider towards the magnetic disk.
The following event will occur when the mass of the magnetic head slider is diminished. It is necessary to reduce the size of a supporting spring which holds the magnetic head slider as the slider is reduced in size. This is intended to maintain the following characteristic with respect to waviness of the disk and maintain the flying stability of the head. The following event will occur when the spring force on the head slider is reduced. That is, the flying stiffness of the head is degraded due to reduction of the spring force on the head slider. Further, the possibility of assembly errors increases because parts, such as a slider and a supporting spring, are diminished in mass. With the above in mind, it is necessary for a device for supporting a magnetic head slider to have a mechanism capable of sufficiently ensuring the flying stability of the magnetic head slider.
Conventionally, the magnetic head supporting mechanism is made up of a load beam, a gimbal fixed to the load beam, and a magnetic head slider fixed to the gimbal. With the above structure, it is more difficult to assemble (position) these parts as the size of the parts is reduced. When there is an assembly error, the magnetic head slider is maintained in an unbalance flying state in which the slider flies in a tilted state. Hence, the reliability of the flying head is degraded and further the read/write characteristics are also degraded. As a result, the reliability of the magnetic disk drive is also degraded.
In order to eliminate the factors causing the unbalanced flying due to the assembly error of the head supporting mechanism, Japanese Patent Laid-Open Application No. 3-189976 proposes an improvement in which an integrally formed supporting spring corresponding to the conventional load beam and gimbal is used and assembly is no longer needed.
FIG. 1 shows a magnetic head supporting mechanism 1 disclosed in the above application document. The magnetic head supporting mechanism 1 includes a load arm 3 and a load beam 4 (which is also referred to as a flexure). The load beam 4 includes a gimbal 5, which has openings (through holes) 6 and 7 having a substantially C shape. Further, the gimbal 5 includes a beam 8 supported at both ends in a direction in which the beam 8 traverses the load beam 4, and tongue portions 9 and 10 extending from the beam 8. The back surface of the magnetic head slider 11 is formed so that grooves are formed in the width direction of the load beam 4.
The magnetic head slider 11 can be rotated together with a twist of the beam 8 in a pitching direction indicated by an arrow 12, and can be rotated together with a bend of the beam 8 in a rolling direction indicated by an arrow 13.
It is necessary to reduce the rotation stiffness of the gimbal 5 in order to ensure the flying stability of the compact magnetic head slider. Further, it is impossible to reduce the thickness t of the gimbal 5 having the above structure because the load beam 4 needs to be stiff. In order to reduce the rotation stiffness of the gimbal 5 without reducing the thickness t of the load beam 4, it is necessary to lengthen the length l of the beam 8. If the load beam 4 and the gimbal 5 are made to have different thicknesses, it is necessary to a complex process in which only the gimbal 5 is half etched, while the load beam is not processed. However, it is very difficult to obtain a desired precision in thickness by the above process and to obtain desirable characteristics.
If the length l of the beam 8 is increased, the following disadvantages will occur. First, the resonance point (frequency) of vibration of the twist and bend of the beam 8 will greatly becomes lower, and it becomes likely that the degree of flying of the magnetic head slider 11 is varied. Second, the width W of the load beam 4 increases, and hence the resonance frequency of vibration of the load beam 4 itself will becomes lower. Thus, the flying magnetic head slider 11 becomes unstable.
Consequently, when the integrally formed supporting spring having the integrated load beam and gimbal is used, it is very difficult to realize a structure of the integrated supporting spring in which only the rotation stiffness is reduced without decreasing the resonance frequency of the gimbal.
It becomes impossible to neglect the influence of lead wires connected to the head because of degradation of the airbearing stiffness caused by down-sizing of the slider and reduction in the load force on the head slider. More particularly, the slider is affected by the stiffness of the lead wires and may cause the slider to fly in the tilt state. Particularly, when a magneto-resistive effect type head (MR head) is used as a reproduction head, such a head is combined with an interactive type head. Hence, four lead wires equal to twice the number of lead wires for the conventional recording/reproducing head are needed. Use of the four lead wires increases the influence of the stiffness of the lead wires. This degrades not only the reliability of the flying head but also the read/write characteristics. Hence, the magnetic disk drive does not have satisfactory reliability.